Magnetic disk drives as a disk device include a disk-shaped recording medium, i.e., a magnetic disk disposed in a case as a disk device and a magnetic head configured to read/write data from/to the magnetic disk. The magnetic head includes, for example, a recording head and reading head (reading element).
In the reading head, when a core width of the reading element is widened, a signal-to-noise (SN) ratio of reading signals is improved because of an averaging effect to media jitter. On the other hand, when the core width of the recording element is widened, a bit error rate is increased because of reading greater signals from adjacent tracks.